Java : File with Examples
Published : September 7, 2023
File (Java SE 20 & JDK 20) API Examples.
You will find code examples on most File methods.
Warning :
- Please see also : Don't use the legacy File class, use new I/O APIs instead
Summary
An abstract representation of file and directory pathnames.
Note :
- Most of the code examples in this article are run on Windows. However, some of the code examples are run on Linux.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.exists()); // false
try (final var writer = new FileWriter(file)) {
writer.write("abc");
writer.write("XYZ");
}
System.out.println(file.exists()); // true
System.out.println(file.isFile()); // true
System.out.println(file.isDirectory()); // false
// --- PowerShell ---
//PS R:\java-work> ls -Name
//aaa.txt
//
//PS R:\java-work> cat aaa.txt
//abcdXYZ
Fields
static final String pathSeparator
The system-dependent path-separator character, represented as a string for convenience.
final var os = System.getProperty("os.name");
System.out.println(os); // Windows 10
System.out.println(File.pathSeparator); // ;
System.out.println(Arrays.toString(File.pathSeparator.getBytes())); // [59]
static final char pathSeparatorChar
The system-dependent path-separator character.
final var os = System.getProperty("os.name");
System.out.println(os); // Windows 10
System.out.println(File.pathSeparatorChar); // ;
final int c = File.pathSeparatorChar;
System.out.println(c); // 59
static final String separator
The system-dependent default name-separator character, represented as a string for convenience.
final var os = System.getProperty("os.name");
System.out.println(os); // Windows 10
System.out.println(File.separator); // \
System.out.println(Arrays.toString(File.separator.getBytes())); // [92]
static final char separatorChar
The system-dependent default name-separator character.
final var os = System.getProperty("os.name");
System.out.println(os); // Windows 10
System.out.println(File.separatorChar); // \
final int c = File.separatorChar;
System.out.println(c); // 92
Constructors
File (File parent, String child)
Creates a new File instance from a parent abstract pathname and a child pathname string.
final var parent = new File("R:\\java-work");
System.out.println(parent); // R:\java-work
final var file = new File(parent, "aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.exists()); // false
System.out.println(file.createNewFile()); // true
System.out.println(file.exists()); // true
File (String pathname)
Creates a new File instance by converting the given pathname string into an abstract pathname.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.exists()); // false
System.out.println(file.createNewFile()); // true
System.out.println(file.exists()); // true
File (String parent, String child)
Creates a new File instance from a parent pathname string and a child pathname string.
final var parent = "R:\\java-work";
System.out.println(parent); // R:\java-work
final var file = new File(parent, "aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.exists()); // false
System.out.println(file.createNewFile()); // true
System.out.println(file.exists()); // true
File (URI uri)
Creates a new File instance by converting the given file: URI into an abstract pathname.
final var uri = URI.create("file:///R:/java-work/aaa.txt");
System.out.println(uri); // file:///R:/java-work/aaa.txt
final var file = new File(uri);
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.exists()); // false
System.out.println(file.createNewFile()); // true
System.out.println(file.exists()); // true
Methods
boolean canExecute ()
Tests whether the application can execute the file denoted by this abstract pathname.
// --- Linux Terminal ---
//$ touch sample1.sh
//$ ls -l sample1.sh
//-rw-rw-r-- 1 xxxx xxxx 0 Sep 4 16:27 sample1.sh
final var os = System.getProperty("os.name");
System.out.println(os); // Linux
final var file = new File("sample1.sh");
System.out.println(file); // sample1.sh
System.out.println(file.canExecute()); // false
System.out.println(file.setExecutable(true)); // true
System.out.println(file.canExecute()); // true
// --- Linux Terminal ---
//$ ls -l sample1.sh
//-rwxrw-r-- 1 xxxx xxxx 0 Sep 4 16:27 sample1.sh
// --- Linux Terminal ---
//$ touch sample2.sh
//$ ls -l sample2.sh
//-rw-rw-r-- 1 xxxx xxxx 0 Sep 4 16:31 sample2.sh
final var file = new File("sample2.sh");
System.out.println(file); // sample2.sh
System.out.println(file.canExecute()); // false
System.out.println(file.setExecutable(true, false)); // true
System.out.println(file.canExecute()); // true
// --- Linux Terminal ---
//$ ls -l sample2.sh
//-rwxrwxr-x 1 xxxx xxxx 0 Sep 4 16:31 sample2.sh
boolean canRead ()
Tests whether the application can read the file denoted by this abstract pathname.
// --- Linux Terminal ---
//$ touch sample1.txt
//$ ls -l sample1.txt
//-rw-rw-r-- 1 xxxx xxxx 0 Sep 4 16:54 sample1.txt
final var os = System.getProperty("os.name");
System.out.println(os); // Linux
final var file = new File("sample1.txt");
System.out.println(file); // sample1.txt
System.out.println(file.canRead()); // true
System.out.println(file.setReadable(false)); // true
System.out.println(file.canRead()); // false
// --- Linux Terminal ---
//$ ls -l sample1.txt
//--w-rw-r-- 1 xxxx xxxx 0 Sep 4 16:54 sample1.txt
// --- Linux Terminal ---
//$ touch sample2.txt
//$ ls -l sample2.txt
//-rw-rw-r-- 1 xxxx xxxx 0 Sep 4 17:01 sample2.txt
final var file = new File("sample2.txt");
System.out.println(file); // sample2.txt
System.out.println(file.canRead()); // true
System.out.println(file.setReadable(false, false)); // true
System.out.println(file.canRead()); // false
// --- Linux Terminal ---
//$ ls -l sample2.txt
//--w--w---- 1 xxxx xxxx 0 Sep 4 17:01 sample2.txt
boolean canWrite ()
Tests whether the application can modify the file denoted by this abstract pathname.
// --- Linux Terminal ---
//$ touch sample1.txt
//$ ls -l sample1.txt
//-rw-rw-r-- 1 xxxx xxxx 0 Sep 4 17:04 sample1.txt
final var os = System.getProperty("os.name");
System.out.println(os); // Linux
final var file = new File("sample1.txt");
System.out.println(file); // sample1.txt
System.out.println(file.canWrite()); // true
System.out.println(file.setWritable(false)); // true
System.out.println(file.canWrite()); // false
// --- Linux Terminal ---
//$ ls -l sample1.txt
//-r--rw-r-- 1 xxxx xxxx 0 Sep 4 17:04 sample1.txt
// --- Linux Terminal ---
//$ touch sample2.txt
//$ ls -l sample2.txt
//-rw-rw-r-- 1 xxxx xxxx 0 Sep 4 17:05 sample2.txt
final var file = new File("sample2.txt");
System.out.println(file); // sample2.txt
System.out.println(file.canWrite()); // true
System.out.println(file.setWritable(false, false)); // true
System.out.println(file.canWrite()); // false
// --- Linux Terminal ---
//$ ls -l sample2.txt
//-r--r--r-- 1 xxxx xxxx 0 Sep 4 17:05 sample2.txt
int compareTo (File pathname)
Compares two abstract pathnames lexicographically.
final var os = System.getProperty("os.name");
System.out.println(os); // Windows 10
// Windows is not case-sensitive.
final var file1 = new File("aaa.txt");
final var file2 = new File("AAA.txt");
System.out.println(file1); // aaa.txt
System.out.println(file2); // AAA.txt
System.out.println(file1.compareTo(file2)); // 0
final var file1 = new File("aaa.txt");
final var file2 = new File("bbb.txt");
System.out.println(file1); // aaa.txt
System.out.println(file2); // bbb.txt
System.out.println(file1.compareTo(file2)); // -1
System.out.println(file2.compareTo(file1)); // 1
boolean createNewFile ()
Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.exists()); // false
System.out.println(file.createNewFile()); // true
System.out.println(file.exists()); // true
System.out.println(file.createNewFile()); // false
static File createTempFile (String prefix, String suffix)
Creates an empty file in the default temporary-file directory, using the given prefix and suffix to generate its name.
final var ret1 = File.createTempFile("prefix-", "-suffix");
System.out.println(ret1); // C:\Users\xxx\AppData\Local\Temp\prefix-1788635824849128964-suffix
final var ret2 = File.createTempFile("abcd-", ".txt");
System.out.println(ret2); // C:\Users\xxx\AppData\Local\Temp\abcd-2471973508160575501.txt
final var ret3 = File.createTempFile("prefix-", null);
System.out.println(ret3); // C:\Users\xxx\AppData\Local\Temp\prefix-4955106351488410780.tmp
static File createTempFile (String prefix, String suffix, File directory)
Creates a new empty file in the specified directory, using the given prefix and suffix strings to generate its name.
final var dir = new File("R:\\java-work");
System.out.println(dir); // R:\java-work
System.out.println(dir.isDirectory()); // true
final var ret1 = File.createTempFile("prefix-", "-suffix", dir);
System.out.println(ret1); // R:\java-work\prefix-11985693266629058833-suffix
final var ret2 = File.createTempFile("abcd-", ".txt", dir);
System.out.println(ret2); // R:\java-work\abcd-17241334720235449415.txt
final var ret3 = File.createTempFile("prefix-", null, dir);
System.out.println(ret3); // R:\java-work\prefix-16933306792652896919.tmp
boolean delete ()
Deletes the file or directory denoted by this abstract pathname.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
final var dir = new File("R:\\java-work\\dir");
System.out.println(dir); // R:\java-work\dir
System.out.println(file.createNewFile()); // true
System.out.println(dir.mkdir()); // true
// --- PowerShell ---
//PS R:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode Name
//---- ----
//d---- dir
//-a--- aaa.txt
System.out.println(file.delete()); // true
System.out.println(file.exists()); // false
//PS R:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode Name
//---- ----
//d---- dir
System.out.println(dir.delete()); // true
System.out.println(dir.exists()); // false
// --- PowerShell ---
//PS R:\java-work> ls
//<No files / directories>
// --- PowerShell ---
//PS R:\java-work> tree /F
//...
//R:.
//└─dir
// aaa.txt
// bbb.txt
final var dir = new File("R:\\java-work\\dir");
System.out.println(dir); // R:\java-work\dir
System.out.println(dir.isDirectory()); // true
System.out.println(dir.delete()); // false
void deleteOnExit ()
Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates.
public class Main {
public static void main(String[] args) throws IOException {
final var file = new File("sample.txt");
System.out.println("file = " + file);
System.out.println("file.exists = " + file.exists());
file.deleteOnExit();
System.out.println("deleteOnExit : OK!");
System.out.println("file.exists = " + file.exists());
}
}
// --- PowerShell ---
//PS R:\java-work> ls -Name
//Main.java
//sample.txt
//
//PS R:\java-work> java Main.java
//file = sample.txt
//file.exists = true
//deleteOnExit : OK!
//file.exists = true
//
//PS R:\java-work> ls -Name
//Main.java
boolean equals (Object obj)
Tests this abstract pathname for equality with the given object.
final var os = System.getProperty("os.name");
System.out.println(os); // Windows 10
// Windows is not case-sensitive.
final var file1 = new File("aaa.txt");
final var file2 = new File("AAA.txt");
System.out.println(file1); // aaa.txt
System.out.println(file2); // AAA.txt
System.out.println(file1.equals(file2)); // true
final var file1 = new File("aaa.txt");
final var file2 = new File("bbb.txt");
System.out.println(file1); // aaa.txt
System.out.println(file2); // bbb.txt
System.out.println(file1.equals(file2)); // false
System.out.println(file2.equals(file1)); // false
boolean exists ()
Tests whether the file or directory denoted by this abstract pathname exists.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
final var dir = new File("R:\\java-work\\dir");
System.out.println(dir); // R:\java-work\dir
final var nonExistentPath = new File("R:\\java-work\\xxx");
System.out.println(nonExistentPath); // R:\java-work\xxx
System.out.println(file.createNewFile()); // true
System.out.println(dir.mkdir()); // true
// --- PowerShell ---
//PS R:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode Name
//---- ----
//d---- dir
//-a--- aaa.txt
System.out.println(file.isFile()); // true
System.out.println(file.isDirectory()); // false
System.out.println(file.exists()); // true
System.out.println(dir.isFile()); // false
System.out.println(dir.isDirectory()); // true
System.out.println(dir.exists()); // true
System.out.println(nonExistentPath.isFile()); // false
System.out.println(nonExistentPath.isDirectory()); // false
System.out.println(nonExistentPath.exists()); // false
File getAbsoluteFile ()
Returns the absolute form of this abstract pathname.
public class Main {
public static void main(String[] args) throws IOException {
final var userDir = System.getProperty("user.dir");
System.out.println("user.dir = " + userDir);
{
final var file = new File("aaa.txt");
System.out.println("------");
System.out.println("file = " + file);
System.out.println("isAbsolute = " + file.isAbsolute());
System.out.println("getAbsoluteFile = " + file.getAbsoluteFile());
System.out.println("getAbsolutePath = " + file.getAbsolutePath());
}
{
final var file = new File("R:\\java-work\\bbb.txt");
System.out.println("------");
System.out.println("file = " + file);
System.out.println("isAbsolute = " + file.isAbsolute());
System.out.println("getAbsoluteFile = " + file.getAbsoluteFile());
System.out.println("getAbsolutePath = " + file.getAbsolutePath());
}
}
}
// --- PowerShell ---
//PS R:\java-work> java Main.java
//user.dir = R:\java-work
//------
//file = aaa.txt
//isAbsolute = false
//getAbsoluteFile = R:\java-work\aaa.txt
//getAbsolutePath = R:\java-work\aaa.txt
//------
//file = R:\java-work\bbb.txt
//isAbsolute = true
//getAbsoluteFile = R:\java-work\bbb.txt
//getAbsolutePath = R:\java-work\bbb.txt
String getAbsolutePath ()
Returns the absolute pathname string of this abstract pathname.
Please see getAbsoluteFile().
File getCanonicalFile ()
Returns the canonical form of this abstract pathname.
public class Main {
public static void main(String[] args) throws IOException {
final var userDir = System.getProperty("user.dir");
System.out.println("user.dir = " + userDir);
{
final var file = new File("dir\\aaa.txt");
System.out.println("------");
System.out.println("file = " + file);
System.out.println("getCanonicalFile = " + file.getCanonicalFile());
System.out.println("getCanonicalPath = " + file.getCanonicalPath());
}
{
final var file = new File("dir\\..\\bbb.txt");
System.out.println("------");
System.out.println("file = " + file);
System.out.println("getCanonicalFile = " + file.getCanonicalFile());
System.out.println("getCanonicalPath = " + file.getCanonicalPath());
}
}
}
// --- PowerShell ---
//PS R:\java-work> java Main.java
//user.dir = R:\java-work
//------
//file = dir\aaa.txt
//getCanonicalFile = R:\java-work\dir\aaa.txt
//getCanonicalPath = R:\java-work\dir\aaa.txt
//------
//file = dir\..\bbb.txt
//getCanonicalFile = R:\java-work\bbb.txt
//getCanonicalPath = R:\java-work\bbb.txt
String getCanonicalPath ()
Returns the canonical pathname string of this abstract pathname.
Please see getCanonicalFile().
long getFreeSpace ()
Returns the number of unallocated bytes in the partition named by this abstract path name.
final var file = new File("D:");
System.out.println(file); // D:
// --- PowerShell ---
//PS R:\java-work> Get-PSDrive D
//
//Name Used (GB) Free (GB) Provider Root ...
//---- --------- --------- -------- ---- ...
//D 1665.41 197.48 FileSystem D:\ ...
System.out.println(file.getTotalSpace()); // 2000263573504
System.out.println(file.getFreeSpace()); // 212039778304
System.out.println(file.getUsableSpace()); // 212039778304
String getName ()
Returns the name of the file or directory denoted by this abstract pathname.
final var file = new File("dir1\\dir2\\aaa.txt");
System.out.println(file.getPath()); // dir1\dir2\aaa.txt
System.out.println(file.getName()); // aaa.txt
System.out.println(file.getParent()); // dir1\dir2
String getParent ()
Returns the pathname string of this abstract pathname's parent, or null if this pathname does not name a parent directory.
Please see getName().
File getParentFile ()
Returns the abstract pathname of this abstract pathname's parent, or null if this pathname does not name a parent directory.
final var file = new File("dir1\\dir2\\aaa.txt");
System.out.println(file); // dir1\dir2\aaa.txt
final var parent = file.getParentFile();
System.out.println(parent); // dir1\dir2
final var parentParent = parent.getParentFile();
System.out.println(parentParent); // dir1
String getPath ()
Converts this abstract pathname into a pathname string.
Please see getName().
long getTotalSpace ()
Returns the size of the partition named by this abstract pathname.
Please see getFreeSpace().
long getUsableSpace ()
Returns the number of bytes available to this virtual machine on the partition named by this abstract pathname.
Please see getFreeSpace().
int hashCode ()
Computes a hash code for this abstract pathname.
final var os = System.getProperty("os.name");
System.out.println(os); // Windows 10
// Windows is not case-sensitive.
final var ret1 = new File("aaa.txt").hashCode();
System.out.println(ret1); // -1239232814
final var ret2 = new File("AAA.TXT").hashCode();
System.out.println(ret2); // -1239232814
final var ret1 = new File("dir1\\dir2\\aaa.txt").hashCode();
System.out.println(ret1); // -639828267
final var ret2 = new File("R:\\java-work\\aaa.txt").hashCode();
System.out.println(ret2); // 503453694
boolean isAbsolute ()
Tests whether this abstract pathname is absolute.
Please see getAbsoluteFile().
boolean isDirectory ()
Tests whether the file denoted by this abstract pathname is a directory.
Please see exists().
boolean isFile ()
Tests whether the file denoted by this abstract pathname is a normal file.
Please see exists().
boolean isHidden ()
Tests whether the file named by this abstract pathname is a hidden file.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.createNewFile()); // true
System.out.println(file.isHidden()); // false
// --- PowerShell ---
//PS R:\java-work> ls -Force | Format-Table -Property Mode, Name
//
//Mode Name
//---- ----
//-a--- aaa.txt
Files.setAttribute(file.toPath(), "dos:hidden", true);
System.out.println(file.isHidden()); // true
// --- PowerShell ---
//PS R:\java-work> ls -Force | Format-Table -Property Mode, Name
//
//Mode Name
//---- ----
//-a-h- aaa.txt
long lastModified ()
Returns the time that the file denoted by this abstract pathname was last modified.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.createNewFile()); // true
final var zoneId = ZoneId.systemDefault();
System.out.println(zoneId); // Asia/Tokyo
final var dateTime1 = ZonedDateTime.of(2100, 1, 1, 0, 0, 0, 0, zoneId);
System.out.println(dateTime1); // 2100-01-01T00:00+09:00[Asia/Tokyo]
final var ret = file.setLastModified(dateTime1.toInstant().toEpochMilli());
System.out.println(ret); // true
// --- PowerShell ---
//PS R:\java-work> ls | Format-Table -Property LastWriteTime, Name
//
//LastWriteTime Name
//------------- ----
//2100/01/01 0:00:00 aaa.txt
final var lastModified = file.lastModified();
System.out.println(lastModified); // 4102412400000
final var dateTime2 = ZonedDateTime.ofInstant(
Instant.ofEpochMilli(lastModified), zoneId);
System.out.println(dateTime2); // 2100-01-01T00:00+09:00[Asia/Tokyo]
long length ()
Returns the length of the file denoted by this abstract pathname.
// --- PowerShell ---
//PS R:\java-work> tree /F
//...
//R:.
//│ aaa.txt
//│ bbb.txt
//│
//└─dir
// ccc.txt
//
//PS R:\java-work> ls | Format-Table -Property Length, Name
//
//Length Name
//------ ----
// dir
//5 aaa.txt
//1000 bbb.txt
//
//PS R:\java-work> ls dir | Format-Table -Property Length, Name
//
//Length Name
//------ ----
// 12 ccc.txt
final var file1 = new File("R:\\java-work\\aaa.txt");
System.out.println(file1); // R:\java-work\aaa.txt
System.out.println(file1.length()); // 5
final var file2 = new File("R:\\java-work\\bbb.txt");
System.out.println(file2); // R:\java-work\bbb.txt
System.out.println(file2.length()); // 1000
final var dir = new File("R:\\java-work\\dir");
System.out.println(dir); // R:\java-work\dir
System.out.println(dir.length()); // 0
String[] list ()
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname.
// --- PowerShell ---
//PS R:\java-work> tree /F
//...
//R:.
//│ aaa.txt
//│ bbb.txt
//│
//└─dir
// ccc.txt
// ddd.txt
{
final var dir = new File("R:\\java-work");
System.out.println(dir); // R:\java-work
final var ret = dir.list();
System.out.println(Arrays.toString(ret)); // [aaa.txt, bbb.txt, dir]
}
{
final var dir = new File("R:\\java-work\\dir");
System.out.println(dir); // R:\java-work\dir
final var ret = dir.list();
System.out.println(Arrays.toString(ret)); // [ccc.txt, ddd.txt]
}
String[] list (FilenameFilter filter)
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
// --- PowerShell ---
//PS R:\java-work> ls -Name
//aaa.txt
//bbb.jpg
//ccc.txt
//ddd.jpg
final var dir = new File("R:\\java-work");
System.out.println(dir); // R:\java-work
final var filter = new FilenameFilter() {
@Override
public boolean accept(File dir, String name) {
return name.endsWith(".txt");
}
};
final var ret1 = dir.list();
System.out.println(Arrays.toString(ret1)); // [aaa.txt, bbb.jpg, ccc.txt, ddd.jpg]
final var ret2 = dir.list(filter);
System.out.println(Arrays.toString(ret2)); // [aaa.txt, ccc.txt]
File[] listFiles ()
Returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname.
// --- PowerShell ---
//PS R:\java-work> tree /F
//...
//R:.
//│ aaa.txt
//│ bbb.txt
//│
//└─dir
// ccc.txt
// ddd.txt
{
final var dir = new File("R:\\java-work");
System.out.println(dir); // R:\java-work
final var files = dir.listFiles();
if (files != null) {
System.out.println("-- listFiles --");
for (final var file : files) {
System.out.println(file);
}
}
// Result
// ↓
//-- listFiles --
//R:\java-work\aaa.txt
//R:\java-work\bbb.txt
//R:\java-work\dir
}
{
final var dir = new File("R:\\java-work\\dir");
System.out.println(dir); // R:\java-work\dir
final var files = dir.listFiles();
if (files != null) {
System.out.println("-- listFiles --");
for (final var file : files) {
System.out.println(file);
}
}
// Result
// ↓
//-- listFiles --
//R:\java-work\dir\ccc.txt
//R:\java-work\dir\ddd.txt
}
File[] listFiles (FileFilter filter)
Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
// --- PowerShell ---
//PS R:\java-work> ls -Name
//aaa.txt
//bbb.jpg
//ccc.txt
//ddd.jpg
final var dir = new File("R:\\java-work");
System.out.println(dir); // R:\java-work
final var filter = new FileFilter() {
@Override
public boolean accept(File pathname) {
return pathname.getName().endsWith(".txt");
}
};
final var files = dir.listFiles(filter);
if (files != null) {
System.out.println("-- listFiles --");
for (final var file : files) {
System.out.println(file);
}
}
// Result
// ↓
//-- listFiles --
//R:\java-work\aaa.txt
//R:\java-work\ccc.txt
File[] listFiles (FilenameFilter filter)
Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
// --- PowerShell ---
//PS R:\java-work> ls -Name
//aaa.txt
//bbb.jpg
//ccc.txt
//ddd.jpg
final var dir = new File("R:\\java-work");
System.out.println(dir); // R:\java-work
final var filter = new FilenameFilter() {
@Override
public boolean accept(File dir, String name) {
return name.endsWith(".txt");
}
};
final var files = dir.listFiles(filter);
if (files != null) {
System.out.println("-- listFiles --");
for (final var file : files) {
System.out.println(file);
}
}
// Result
// ↓
//-- listFiles --
//R:\java-work\aaa.txt
//R:\java-work\ccc.txt
static File[] listRoots ()
List the available filesystem roots.
final var roots = File.listRoots();
for (final var root : roots) {
System.out.println(root);
}
// Result
// ↓
//C:\
//D:\
//...
boolean mkdir ()
Creates the directory named by this abstract pathname.
// --- PowerShell ---
//PS R:\java-work> ls -Name
//<No files / directories>
final var dir1 = new File("R:\\java-work\\dir1");
System.out.println(dir1); // R:\java-work\dir1
System.out.println(dir1.mkdir()); // true
// --- PowerShell ---
//PS R:\java-work> tree /F
//...
//R:.
//└─dir1
final var dir2 = new File(dir1, "dir2");
System.out.println(dir2); // R:\java-work\dir1\dir2
System.out.println(dir2.mkdir()); // true
// --- PowerShell ---
//PS R:\java-work> tree /F
//...
//R:.
//└─dir1
// └─dir2
// --- PowerShell ---
//PS R:\java-work> ls -Name
//<No files / directories>
final var dir = new File("R:\\java-work\\dir1\\dir2");
System.out.println(dir); // R:\java-work\dir1\dir2
System.out.println(dir.mkdir()); // false
// --- PowerShell ---
//PS R:\java-work> ls -Name
//<No files / directories>
boolean mkdirs ()
Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories.
// --- PowerShell ---
//PS R:\java-work> ls -Name
//<No files / directories>
final var dir = new File("R:\\java-work\\dir1\\dir2");
System.out.println(dir); // R:\java-work\dir1\dir2
System.out.println(dir.mkdirs()); // true
// --- PowerShell ---
//PS R:\java-work> tree /F
//...
//R:.
//└─dir1
// └─dir2
boolean renameTo (File dest)
Renames the file denoted by this abstract pathname.
final var src = new File("R:\\java-work\\src.txt");
System.out.println(src); // R:\java-work\src.txt
final var dst = new File("R:\\java-work\\dst.txt");
System.out.println(dst); // R:\java-work\dst.txt
System.out.println(src.exists()); // true
System.out.println(dst.exists()); // false
// --- PowerShell ---
//PS R:\java-work> ls -Name
//src.txt
//PS R:\java-work> cat src.txt
//abcd
System.out.println(src.renameTo(dst)); // true
System.out.println(src.exists()); // false
System.out.println(dst.exists()); // true
// --- PowerShell ---
//PS R:\java-work> ls -Name
//dst.txt
//PS R:\java-work> cat dst.txt
//abcd
boolean setExecutable (boolean executable)
A convenience method to set the owner's execute permission for this abstract pathname.
Please see canExecute().
boolean setExecutable (boolean executable, boolean ownerOnly)
Sets the owner's or everybody's execute permission for this abstract pathname.
Please see canExecute().
boolean setLastModified (long time)
Sets the last-modified time of the file or directory named by this abstract pathname.
Please see lastModified().
boolean setReadable (boolean readable)
A convenience method to set the owner's read permission for this abstract pathname.
Please see canRead().
boolean setReadable (boolean readable, boolean ownerOnly)
Sets the owner's or everybody's read permission for this abstract pathname.
Please see canRead().
boolean setReadOnly ()
Marks the file or directory named by this abstract pathname so that only read operations are allowed.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
System.out.println(file.createNewFile()); // true
// --- PowerShell ---
//PS R:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode Name
//---- ----
//-a--- aaa.txt
System.out.println(file.setReadOnly()); // true
// --- PowerShell ---
//PS R:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode Name
//---- ----
//-ar-- aaa.txt
boolean setWritable (boolean writable)
A convenience method to set the owner's write permission for this abstract pathname.
Please see canWrite().
boolean setWritable (boolean writable, boolean ownerOnly)
Sets the owner's or everybody's write permission for this abstract pathname.
Please see canWrite().
Path toPath ()
Returns a java.nio.file.Path object constructed from this abstract path.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
final var path = file.toPath();
System.out.println(path); // R:\java-work\aaa.txt
Files.writeString(path, "abcd");
// --- PowerShell ---
//PS R:\java-work> ls -Name
//aaa.txt
//PS R:\java-work> cat aaa.txt
//abcd
String toString ()
Returns the pathname string of this abstract pathname.
final var file = new File("aaa.txt");
final var str = file.toString();
System.out.println(str); // aaa.txt
final var dir = new File("R:\\java-work\\dir");
final var str = dir.toString();
System.out.println(str); // R:\java-work\dir
URI toURI ()
Constructs a file: URI that represents this abstract pathname.
final var file = new File("R:\\java-work\\aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt
final var uri = file.toURI();
System.out.println(uri); // file:/R:/java-work/aaa.txt
URL toURL ()
Deprecated. This method does not automatically escape characters that are illegal in URLs.
Deprecated.